RAINWATER, SOIL AND NUTRIENT CONSERVATION IN RAIN-FED RICE LANDS IN EASTERN INDIA

In rainfed rice ecosystem, conservation of rainwater to maximum extent can reduce the supplemental irrigation water requirement of the crop and drainage need of the catchment. The results of 3 years of experime ntal study on the above stated aspects in diked rice fields with vario us weir heights (6-30 cm at an interval of 4 cm) revealed that about 5 6.75% and 99.5% of the rainfall can be stored in 6 and 30 cm weir heig ht plots, respectively. Sediment losses of 347.8 kg/ha and 3.3 kg/ha h ave been recorded in runoff water coming out of 6 cm and 30 cm weir he ight plots, respectively in a cropping season. Similarly, total Kjelda hl nitrogen (TKN) loss in runoff water from rice field ranged from 4.2 3 kg/ha (6 cm weir height plots) to 0.17 kg/ha (26 cm weir height plot s) and available potassium loss ranged from 2.20 kg/ha (6 cm weir heig ht plots) to 0.04 kg/ha (30 cm weir height plots). Conservation of rai nwater in rice fields with various weir heights could not create any s ignificant impact on grain yield differences, leaf area index and othe r biometric characters. Irrigation requirement of 18 cm and above weir height plots was found to be half of the requirement of 6 cm weir hei ght plots. Keeping in view the aspects of conserving rainwater, sedime nt and nutrient and minimizing irrigation requirement, 22-26 cm of dik e height is considered to be suitable for rice fields of Bhubaneswar r egion. (C) 1998 Elsevier Science B.V. All rights reserved.